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Help with MC 2125

bendoggie

bendoggie

Active Member
First hello to all in Mcintosh land. About a year ago I finally got the chance to purchase a mint condition set. A C32 pre and A MC 2125. They look brand new. The man I purchased them from had them gone over by a fella named Tom Manley then they sat unused for five years. He had lots of Mc gear. Now however I am having a problem with the amp. I am driving a pair of Reference 3a serie master speakers and I loose the left channel or it just goes low in volume with static. If I shut it off and turn it on or cycle the speaker mute switch the channel comes back. If I raise the volume high it will suddenly play right. I tried it with a Nak pre and the same happens, so it is the amp. I started to take it apart to clean the switch but I stopped because I dont know if the bottom cover will just come off as it wraps up on both sides. Any suggestions will be greatly appreciated as I love these and want them right.
 
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The bottom cover comes off the way you assumed - cinch. Just remove the hex head screws on the sides retaining it. Also I believe you are on the correct track chasing down a dirty switch or control. Clean 'em all while you've got the bottom panel off (including the slide switches on the rear panel).

There is a sticky in the forum somewhere about DeOxit and how to use it. You may want to read that first.

Do report back.
 
Clean the speaker terminals also and you might want to do that first. Also just try switching your speaker wires to see if the issues follows or remans in the same channel
 
Help with MC2125

Hello

Your trouble is coming from the speaker relay .

Just change it and everything will go back to normal function !

To take the bottom cover off you have 3 screws on the left side , 3 screws on the right side and 6 screws (I think) on the cover
 
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I agree- speaker relay!

Easy enough to buy one and change. Symptoms are exactly what mine was doing.
 
Thanks for the info... Im going for the speaker relay....everything inside the amp is so incredibly clean that I cant beleive its a switch.
 
bendoggie said:
Thanks for the info... Im going for the speaker relay....everything inside the amp is so incredibly clean that I cant beleive its a switch.
Click to expand...

I've been told speaker relay develops corrosion from arcing from switching speakers on/off at high output.
 
update

It was the relay. I removed it just enough that I did not have to unsolder the coil connections and it opened easily. Cleaned the contacts with folded emery cloth and then gave them a shot of deoxit. SOUNDS GREAT !
Thanks to all that responded, I love AK:banana:
 
The relay is self wiping by design, no use for several years causes oxidation to build up on the contacts that never gets wiped off thru use. The cleaning you gave it was what was needed to get it working again, and with regular use they should stay clean, this is a typical 'use it or loose it' situation that happens commonly when people have a large collection that rarely gets used.
 
Terry - That's a great tidbit there. I had no idea that was the case.

OP - glad the fix was easy. Post a pic or two of your setup.
 
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